Systems and methods for monitoring ablation progress using linear EBUS data

Abstract

A system and method are presented for treating targeted tissue using cryoablation. A linear endobronchial ultrasound (EBUS) device is positioned adjacent the targeted tissue and is used to guide a percutaneously inserted cryoprobe into the targeted tissue. The EBUS device is partially rotated in order to create multiple image slices that are combined together. To overcome the acoustic shadow created by the ice ball, a 3D model is created of the ice ball based on the locations identified on visible portion of the ice ball's peripheral surface. These locations are mirrored across an axis defined for the cryoprobe to define an approximate location for the hidden, non-visible periphery. This model is then displayed along with the location of the targeted tissue and an indication of the killing zone of the ice ball defined by a selected isotherm.

What is claimed is: 
     
       1. A method for treating a patient comprising:
 a) placing an ultrasound device in a trachea-bronchial tree of the patient in position to image a targeted tissue; 
 b) placing a cryoprobe into the targeted tissue; 
 c) generating an ice ball by cooling the cryoprobe; and 
 d) while generating the ice ball:
 i) rotating the ultrasound device to create multiple 2D image slices of the targeted tissue, 
 ii) using a computer, combining the multiple 2D image slices to identify a visible surface of the ice ball, 
 iii) using the computer, generating a 3D model of the ice ball based on the visible surface, 
 iv) using the computer, generating an isotherm for the 3D model at a selected temperature identified for effective ablation, and 
 v) using the computer, displaying on a user interface the 3D model of the ice ball and the isotherm. 
 
 
     
     
       2. The method of  claim 1 , wherein the ultrasound device is a linear endobronchial ultrasound (EBUS) device. 
     
     
       3. The method of  claim 2 , wherein the linear EBUS device has a plurality of ultrasound transducer elements; further wherein the plurality of ultrasound transducer elements are of a type selected from a set consisting of PZT based-transducers, pMUT based-transducers, and cMUT based-transducers. 
     
     
       4. The method of  claim 1 , further comprising displaying on the user interface a representation of the targeted tissue relative to the 3D model of the ice ball and the isotherm. 
     
     
       5. The method of  claim 1  further comprising comparing on the computer the 3D model of the ice ball against a known size and shape of the targeted tissue to identify portions of the targeted tissue outside the isotherm; and displaying the identified portions of the targeted tissue on the user interface using an identifiable distinguishing visual characteristic. 
     
     
       6. The method of  claim 1 , wherein a distal end of the ultrasound device further contains electromagnetic sensors that receive electromagnetic signals that locate the distal end in an electromagnetic field, and further comprising using the electromagnetic signals to display on the user interface the 3D model of the ice ball on a representation of the targeted tissue. 
     
     
       7. The method of  claim 1 , wherein the 3D model of the ice ball and the isotherm displayed on the user interface change over time in response to an increase in size of the ice ball. 
     
     
       8. The method of  claim 1 , further comprising terminating generation of the ice ball prior to an anticipated termination time when the user interface indicates that the isotherm encompasses the targeted tissue. 
     
     
       9. The method of  claim 1 , further comprising continuing generation of the ice ball beyond an anticipated termination time when the user interface indicates that the isotherm fails to encompass the targeted tissue. 
     
     
       10. The method of  claim 1 , wherein generating of the 3D model comprises:
 i) identifying an axis for the cryoprobe, 
 ii) identifying 3D positions on the visible surface of the ice ball, 
 iii) reflecting the identified 3D positions across the axis for the cryoprobe to identify points on a hidden surface of the ice ball, and 
 iv) combining the 3D positions on the visible surface with the identified points on the hidden surface. 
 
     
     
       11. The method of  claim 10 , wherein reflecting the identified 3D positions across the axis for the cryoprobe takes place perpendicularly from the axis and the points are equidistance from the axis as the identified 3D positions. 
     
     
       12. The method of  claim 10 , wherein only a selected number of 3D positions are reflected, and the 3D model approximates positions between the selected number of 3D positions on the visible surface and the points on the hidden surface. 
     
     
       13. The method of  claim 1 , wherein generating the isotherm for the 3D model at the selected temperature comprises:
 i) identifying a known distance from a perimeter of the ice ball known to be at the selected temperature or colder; 
 ii) identifying the isotherm that is at that known distance from the perimeter of the ice ball. 
 
     
     
       14. The method of  claim 13 , wherein in the known distance is determined through testing of temperatures in cryoablation tests. 
     
     
       15. The method of  claim 13 , further comprising requiring that the selected temperature or colder be sustained for a determined time period. 
     
     
       16. The method of  claim 15 , wherein the determined time period is at least three minutes. 
     
     
       17. A system comprising:
 a) a cryoprobe; 
 b) an ultrasound device; 
 c) a display; 
 d) a computer system in communication with the cryoprobe, the ultrasound device, and the display, the computer system having a processor operating under programming, the programming causing the computer system to:
 i) receive 2D image slices of targeted tissue in a patient from the ultrasound device as it rotates within the patient, the 2D image slices containing representations of an ice ball as being formed by the cryoprobe, 
 ii) combine the 2D image slices to identify a visible surface of the ice ball, 
 iii) generate a 3D model of the ice ball based on the visible surface, 
 iv) generate an isotherm for the 3D model of the ice ball at a selected temperature identified for effective ablation, and 
 v) generate on the display a user interface showing the 3D model of the ice ball and the isotherm. 
 
 
     
     
       18. The system of  claim 17 , further wherein the computer system contains a model of the targeted tissue registered to the patient, still further wherein the user interface shows a representation of the targeted tissue relative to the 3D model of the ice ball and the isotherm. 
     
     
       19. The system of  claim 18 , wherein the programming further causes the computer system to compare the 3D model of the ice ball against a known size and shape of the targeted tissue to identify portions of the targeted tissue outside the isotherm; and further wherein shows the identified portions of the targeted tissue using an identifiable distinguishing visual characteristic. 
     
     
       20. The system of  claim 17 , wherein the programming causes the computer system to generate the 3D model of the ice ball by causing the computer system to:
 i) identify an axis for the cryoprobe, 
 ii) identify 3D positions on the visible surface of the ice ball, 
 iii) reflect the identified 3D positions across the axis for the cryoprobe to identify points on a hidden surface of the ice ball, and 
 iv) combine the 3D positions on the visible surface with the identified points on the hidden surface. 
 
     
     
       21. The system of  claim 20 , wherein the identified 3D positions reflect across the axis for the cryoprobe perpendicularly from the axis and the points are equidistance from the axis as the identified 3D positions. 
     
     
       22. The system of  claim 20 , wherein only a selected number of 3D positions are reflected, and the 3D model of the ice ball approximates positions between the selected number of 3D positions on the visible surface and the points on the hidden surface. 
     
     
       23. The system of  claim 17 , wherein generating the isotherm for the 3D model at the selected temperature comprises:
 i) identifying a known distance from a perimeter of the ice ball known to be at the selected temperature or colder; 
 ii) identifying the isotherm that is at that known distance from the perimeter of the ice ball. 
 
     
     
       24. The system of  claim 23 , wherein in the known distance is determined through testing of temperatures in cryoablation tests. 
     
     
       25. The system of  claim 23 , further comprising requiring that the selected temperature or colder be sustained for a determined time period. 
     
     
       26. The system of  claim 25 , wherein the determined time period is at least three minutes. 
     
     
       27. A computer system in communication with a cryoprobe, ultrasound device, and a display, the computer system comprising:
 a) a processor; and 
 b) programming causing the processor to:
 i) receive 2D image slices of targeted tissue in a patient from the ultrasound device as it rotates within the patient, the 2D image slices containing representations of an ice ball as being formed by the cryoprobe, 
 ii) combine the 2D image slices to identify a visible surface of the ice ball, 
 iii) generate a 3D model of the ice ball based on the visible surface, 
 iv) generate an isotherm for the 3D model of the ice ball at a selected temperature identified for effective ablation, and 
 v) generate on the display a user interface showing the 3D model of the ice ball and the isotherm.